Tumor antigens have been identified in renal cell carcinoma, in the tumor membrane lymphocyte stimulation assay and with autologous antibodies. Stimulation of autologous lymphocytes with tumor plasma membranes provides a unique approach for determining the responding lymphocyte population in vitro and a determination of the responding cells immunological function. A positive in vitro blastogenic response was observed in 1/3 of the patients in these studies. Our studies in vitro demonstrate the responding lymphocytes are primarily T-suppressor cells. Future studies will be directed towards establishing a correlation between the immune response, the responding populations, and the clinical course of the patient. The importance of the genetic restriction of this response and the clinical course of the patient remains to be determined.